TRANSFORMER PROVIDING LOW OUTPUT VOLTAGE

Description

Background of the invention

[0001] The present invention relates to a planar transformer providing low output voltage, particularly a planar transformer for use in DC-DC power converters.

[0002] As microprocessors and other integrated semiconductor devices become denser, it is desirable to lower their supply voltage requirements. Accordingly, supply voltages for digital electronics have been reduced from 5 volts to 3.3 volts, then to 2.5 volts, and are now being reduced to 1.6 volts. The trend is expected to continue.

[0003] A power converter for supplying the integrated circuits typically employs a transformer to accept an input at a relatively high voltage and produce a, lower output voltage. As is well known, standard transformers typically employ a ferrite core around which wires forming primary (input) and,secondary (output) circuits are wound. These standard transformers are notoriously expensive and bulky however, and alternative transformer embodiments have been used in computer power supplies to lower cost and decrease size. One such embodiment is the "planar" transformer, wherein the wires are replaced by traces in one or more layers of a circuit board.

[0004] The prior art transformer has a limitation, in the output voltage that it is capable of producing. Particularly, magnetic technology has typically been limited to the output voltage that is produced by one turn of the secondary. To address this limitation, fractional turns have been employed. Referring to Figure 1 as an example, a core 2 is shown having a center leg 3. around which a primary winding 4 is looped. The core 2 has two secondary "legs" 6a and 6b, and a secondary winding 8 is looped around one of the legs 6a one half-turn. A problem with this transformer is that magnetic flux circulating from the center leg through the other leg 6b leads to an undesirable leakage inductance.

[0005] To address this problem, referring to Figure 2, a half-turn of the secondary 8 is looped around the leg 6a and a half-turn is looped around the leg 6b. The two loops contribute to the total output voltage in parallel, and all of the flux in the core links the secondary. However, a problem remains in that the two legs 6a and 6b are not identical, so that the magnetic flux through the respective half-turns is not identical. In response, an additional circulating current flows in the secondary in order to balance the magnetic flux, leading to additional ohmic power loss.

[0006] Another problem with the prior art as shown in Figure 2 is that the secondary 8 winding is relatively long compared to the secondary winding shown in Figure 1. This also increases ohmic loss in the transformer, and in addition increases stray inductance.

[0007] Accordingly, there is a need for a transformer providing low output voltage that provides for converting substantially all the magnetic flux circulating in the core of a transformer into an output current, particularly by decreasing ohmic loss and stray inductance.

[0008] In the document GB 2 285 892 A a transformer arrangement is shown where some of the windings are implemented as tracks on a PCB. Fig. 3 to 5 illustrate the magnetic core having two leg portions (15, 16) and a central portion (17), where each core portion includes two parts (15a/ 15b, 16a/16b and 17a/ 17b) in order to allow implementation of fractional windings. A first winding is wound around the first leg portion (15a/15b), a second winding around leg portion (16) and a third winding around center portion (17). All three windings are wound around the core portions in the same sense.

[0009] The document US 1 553 983 describes a magnetic core with a T-shaped section (1) and a U-shaped section (2) fitted together to form three legs (6, 7, and 8). A retardation coil (9) is wound around the center portion. Further, a primary winding (10/12) is wound around both outer legs (7 and 8) in different senses and a secondary winding (11/13) is also wound around both outer legs (7 and 8) in different senses.

Summary of the Invention

[0010] The transformer providing low output voltage of the present invention solves the aforementioned problems and, meets the aforementioned needs by providing a magnetic core having at least two apertures defining a center portion between the apertures and two outer leg portions. The core has primary and secondary windings. The primary winding receives a first voltage or current and induces a second voltage or current in the secondary winding. The input power is provided at a higher voltage than the output power, the latter which is preferably less than or substantially equal to 3.3 volts.

[0011] The primary winding has a first portion looped around one of the leg portions so that a current passed through the first winding will produce a magnetic flux in that leg portion that circulates in either the right hand or left hand sense. A second portion of the primary winding is looped around the other leg portion in the opposite sense. This provides for a magnetic flux circulating through the two outer leg portions in the same sense, and provides that the magnetic flux circulating through the center portion is zero. The secondary winding is preferably provided as a fractional loop around one of the outer leg portions.

[0012] Therefore, it is a principal object of the present invention to provide a novel and improved transformer providing low output voltage.

[0013] It is another object of the present invention to provide a transformer providing low output voltage that provides for converting substantially all the magnetic flux circulating' in the core of a transformer into an output current.

[0014] It is yet another object of the present invention to provide a transformer providing low output voltage that provides for high efficiency.

[0015] It is still another object of the invention to provide a transformer providing low output voltage that provides for minimal leakage inductance.

[0016] It is a further object of the present invention to provide a transformer providing low output voltage that provides for minimal ohmic loss.

[0017] It is still a further object of the present invention to provide such a transformer at lower cost.

[0018] The foregoing and other objects, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the-following drawings.

Brief Description of the Drawings 1-10

[0019] 

Figure 1

is a pictorial schematic of a prior art planar transformer shown in horizontal cross-section.

Figure 2

is a pictorial schematic of another prior art planar transformer shown in horizontal cross-section.

Figure 3

is a pictorial schematic of a prior art transformer shown in side elevation.

Figure 4

is a schematic of a circuit equivalent to the prior art transformer of Figure 1.

Figure 5A

is a pictorial schematic of a transformer providing a low output voltage according to the present invention shown in side elevation.

Figure 5B

is a pictorial schematic of the transformer of Figure 5A with the center portion removed.

Figure 6

is a pictorial schematic of a center tap embodiment of a transformer providing a low output voltage according to the present invention shown in horizontal cross-section.

Figure 7

is a pictorial schematic of the center tap embodiment of a transformer providing a low output voltage of Figure 6 in a power converter circuit employing an integrated choke.

Figure 8

is a pictorial schematic of a multiple core embodiment of the transformer of Figure 5.

Figure 9

is a pictorial schematic of a multiple core embodiment of the transformer of Figure 6.

Figure, 10

is a pictorial schematic of a multiple core embodiment of the transformer of Figure 7. ,

Detailed Description of a Preferred Embodiment

[0020] As discussed above, Figures 1 and 2 illustrate prior art transformers providing low output voltage as a result of employing fractional turns or loops in the secondary winding. Shown in Figures 1 and 2 are half-turns; however, other fractions of turns may be employed. Turning to Figure 3, the principal of their operation is clarified to further a comparison with the present invention. A core 2 has a center portion 4 and two leg portions 6a and 6b. A primary winding 8 is coupled to a source of voltage or current P_in. The primary winding is looped around the leg portions so that current i_in flowing through the winding produces a magnetic flux "B₁" in the leg portion 6a and "B₂" in the leg portion 6b. The flux "B₁" circulates in one of the right hand or left hand sense, depending on the direction of the current i_in, and the flux "B₂" circulates in the other sense, so that two independent paths of magnetic flux are operative. Twice the magnetic flux that is present in each leg portion 6 circulates through the center portion 4.

[0021] In an embodiment of the transformer of Figure 3 that corresponds to that of Figure 1, one secondary winding 9a is looped around one of the leg portions 6a. Similarly, in an embodiment of the transformer of Figure 3 corresponding to that of Figure 2, two secondary windings 9a and 9b are looped, respectively, around the leg portions 6a and 6b.

[0022] In the embodiment corresponding to Figure 1, the winding 9a encircles all of the magnetic flux "B₁" but none of the magnetic flux "B₂." The magnetic flux "B₁" is therefore transformed or converted to current flow in the winding 9a wherein the current flows in the winding 9a so as to cancel the magnetic flux "B_1." However, due to the lack of a winding 9b, the magnetic flux "B₂" is not converted to current flow, so that the magnetic flux "B₂" is not canceled and remains in the core, leading to leakage inductance. Figure 4 shows the equivalent circuit of the embodiment of Figure 1, showing the leakage inductance "L."

[0023] Alternatively, in the embodiment of the transformer of Figure 3 that corresponds to that of Figure 2, all of the magnetic flux is transformed or converted to current flow only if perfect symmetry is achieved in the windings 9. Since this is not possible, there remains an uncanceled magnetic flux and consequently a remaining leakage inductance. In addition, connecting the windings 9a and 9b in the manner of the winding 8 in Figure 2 ensures that there will be an increased ohmic loss as well as increased stray inductance.

[0024] Turning now to Figure 5A, a simplified embodiment of a transformer 10 providing low output voltage according to the present invention is shown to illustrate an outstanding principle of the invention. A core 12 has a center portion 14 and two leg portions 16a and 16b. A primary winding 18 is coupled to a source of voltage or current P_in. The primary winding is looped around the leg portions so that current i_in flowing through the winding produces a magnetic flux "B" in each leg portion that circulates in one of either the right hand or left hand sense as shown by the arrows. Because of the novel arrangement of the primary winding 18, no magnetic flux circulates through the center portion 14. Particularly, the primary winding is not wound around the center portion 14 as in the prior art, but is instead wound around the leg portions 16a and 16b.

[0025] A secondary winding 19 may be looped around either or, preferably, both of the leg portions 16. The single turn encloses all of the flux B without the need for creating perfect symmetry in two separate windings. Accordingly, the transformer may be provided with higher efficiency at lower cost, and has a minimal or zero leakage inductance. Turning to Figure 5B, this is particularly so where the center portion 14 has been removed from the core 12. While the center portion may be employed for other purposes, such as described below and such as described in the present inventor's companion application entitled METHOD AND APPARATUS FOR TRANSMITTING A SIGNAL THROUGH A POWER MAGNETIC STRUCTURE, executed on even date herewith, its removal prevents any remaining asymmetry in magnetic flux through the leg portions to lead to leakage inductance by virtue of magnetic flux circulating through the center portion.

[0026] Referring to Figure 6 a "center-tap" embodiment of the invention is shown. The secondary winding 19 forms a figure 8 pattern that results in looping a fractional turn around the leg portion 16a in one of the right or left hand sense, and continues so as to loop a full turn around the other leg portion 16b in the opposite sense. A node 20 lies on the winding 19 forming the center tap with respect to ends B and C. Figure 7 shows the embodiment of Figure 6 configured as a power converter with an integrated output filtering choke 22 employing the center portion 14 of the core 12.

[0027] Turning to Figures 8 - 10, multiple core embodiments of the transformers (and circuits) of Figures 5 - 8, respectively, are shown according to the present invention. The multiple core embodiments are based on the principle that, where there are N cores looped by the primary 18, the voltage induced in the secondary 19 is reduced by a factor of 1 /N. For example, employing 3 cores 12a - 12c as shown in Figure 8, each with half-turn secondary loops 19a - 19c, provides the same output voltage Vout as would a single core transformer employing a one-sixth-turn secondary. Similarly, Figure 9 shows three cores 12a - 12c having respective center taps Aa, Ab and Ac, with respect to respective outputs Ba, Ca; Bb, Cb, and Bc, Cc. In Figure 10, a respective integrated output filtering chokes 22a - 22c provide outputs Vout(a) - Vout(c), which may be connected in parallel to provided a single output voltage. Figure 8 also shows the use of a secondary winding 19 that is looped around two of the leg portions, as mentioned above.

[0028] It is to be recognized that, while a particular transformer providing low output voltage has been shown and described as preferred, other configurations and methods could be utilized, in addition to those already mentioned, without departing from the principles of the invention.

[0029] The terms and expressions which have been employed in the foregoing specification are used therein as terms of description and not of limitation, and there is no intention of the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims which follow.

Claims

1. A transformer for providing a low output voltage, comprising:

- a magnetic core (12) having at least two apertures defining a center portion (14) therebetween and two leg portions (16a,16b);

- a primary winding (18) having a first portion looped around one of said leg portions in either the right or left hand sense, and a second portion looped around the other leg portion in the opposite sense forming a power input; and

- a secondary winding (19) having a first portion looped around one of said leg portions a fractional turn, said secondary winding (19) having two ends forming a first power output.

2. The transformer of claim 1, wherein said first portion of said secondary winding (19) is looped around one of the leg portions in either the right or left hand sense and around the remaining leg portion in the opposite sense, wherein a first node disposed on said secondary winding (19) between said two ends forms a center tap with respect thereto.

3. The transformer of claim 2, further comprising a third winding looped around said center portion (14), said third winding having two ends, wherein said two ends of said secondary winding (19) are coupled together to form a second node, wherein one of said ends of said third winding is coupled to said second node, and wherein the other end of said third winding forms a second power output with respect to said first node.

4. The transformer of claim 3, wherein said third winding is looped round said center portion (14) a fractional turn.

5. A method for providing a low output voltage, comprising the steps of:

- providing a magnetic core (12) having at least two apertures defining a center portion (14) therebetween and two leg portions (16a,16b);

- providing a first portion of a primary winding (18) as being looped around one of said leg portions in one of the right or left hand sense;

- providing a second portion of said primary winding (18) as being looped around the other leg portion in the opposite sense;

- applying a power input to said primary winding (18);

- providing a secondary winding (19) having two ends;

- providing a first portion of said secondary winding (19) as being looped around one or both of said leg portions a fractional turn; and

- thereby, providing a power output across said two ends of said secondary winding (19).

6. The method of claim 5, further comprising providing said power input to be substantially greater than 3.3 volts, and providing said power output to be less than or substantially equal to 3.3 volts.

7. The method of claim 5, further comprising providing said first portion of said secondary winding (19) to be looped around one of the leg portions in either the right or left hand sense and around the remaining leg portion in the opposite sense, and forming a center tap along said secondary winding (19) between said two ends with respect thereto.

8. The method of claim 7, further comprising providing a third winding having two ends and being looped around said center portion (14), coupling said two ends of said secondary winding (19) together to form a second node, coupling one of said ends of said third winding to said second node, and forming a second power output from the other end of said third winding, along with said first node.

9. The method of claim 7, further comprising providing a third winding having two ends and being looped around said center portion (14), coupling said two ends of said secondary winding (19) together to form a second node, coupling one of said ends of said third winding to said second node, and taking a second power output with respect to said first node at the other end of said third winding.

10. The method of claim 5, further comprising providing at least one additional magnetic core having at least two apertures defining a center portion (14) therebetween and two leg portions (16a,16b), providing said first portion of said primary winding (18) as being looped around one of said leg portions of said at least one additional magnetic core in said one of the right or left hand sense, and providing said second portion of said primary winding (18) as being looped around the other leg portion of said at least one additional magnetic core in the opposite sense.

11. The method of claim 10, further comprising providing said first portion of said secondary winding (19) as being looped around said one or both of said leg portions in either the right hand or left hand sense, and providing a first portion of another secondary winding as being looped around one of said leg portions of said at least one additional magnetic core in the same said sense as said first portion of said secondary winding (19), said other secondary winding having two ends coupled in parallel to said two ends of said secondary winding (19).

Ansprüche

1. Transformator zum Bereitstellen einer niedrigen Ausgangsspannung, der Folgendes umfasst:

- einen Magnetkern (12) mit wenigstens zwei Öffnungen, die einen Zentralabschnitt (14) dazwischen begrenzen, und zwei Schenkelabschnitten (16a, 16b);

- eine primäre Wicklung (18) mit einem ersten Abschnitt, der entweder in Rechtsrichtung oder in Linksrichtung um einen der Schenkelabschnitte gewunden ist, und mit einem zweiten Abschnitt, der in der entgegengesetzten Richtung um den anderen Schenkelabschnitt gewunden ist, so dass ein Leistungseingang gebildet ist; und

- eine sekundäre Wicklung (19), die einen ersten Abschnitt aufweist, der in einer Teilwindung um einen der Schenkelabschnitte gewunden ist, wobei die sekundäre Wicklung (19) zwei Enden aufweist, die einen ersten Leistungsausgang bilden.

2. Transformator nach Anspruch 1, wobei der erste Abschnitt der sekundären Wicklung (19) entweder in Rechtsrichtung oder in Linksrichtung um einen der Schenkelabschnitte, und um den verbleibenden Schenkelabschnitt in der entgegengesetzten Richtung gewunden ist, wobei ein erster Knoten, der an der sekundären Wicklung (19) zwischen den zwei Enden angeordnet ist, einen Zentralabzweig in Bezug darauf bildet.

3. Transformator nach Anspruch 2, der außerdem eine dritte Wicklung aufweist, die um den Zentralabschnitt (14) gewunden ist, wobei die dritte Wicklung zwei Enden aufweist, wobei die zwei Enden der sekundären Wicklung (19) aneinander gekoppelt sind, um einen zweiten Knoten zu bilden, wobei eins der Enden der dritten Wicklung an den zweiten Knoten gekoppelt ist, und wobei das andere Ende der dritten Wicklung einen zweiten Leistungsausgang in Bezug auf den ersten Knoten bildet.

4. Transformator nach Anspruch 3, wobei die dritte Wicklung in einer Teilwindung um den Zentralabschnitt (14) gewunden ist.

5. Verfahren zum Bereitstellen einer niedrigen Ausgangsspannung, das folgende Schritte umfasst:

- Bereitstellen eines Magnetkerns (12) mit wenigstens zwei Öffnungen, die einen Zentralabschnitt (14) dazwischen begrenzen, und zwei Schenkelabschnitten (16a, 16b);

- Bereitstellen eines ersten Abschnitts einer primären Wicklung (18) als gewunden um einen der Schenkelabschnitte entweder in Rechtsrichtung oder in Linksrichtung;

- Bereitstellen eines zweiten Abschnitts der primären Wicklung (18) als gewunden um den anderen Schenkelabschnitt in der entgegengesetzten Richtung;

- Anlegen eines Leistungseingangs an die primäre Wicklung (18);

- Bereitstellen einer sekundären Wicklung (19) mit zwei Enden;

- Bereitstellen eines ersten Abschnitts der sekundären Wicklung (19) als gewunden in einer Teilwindung um einen oder beide Schenkelabschnitte; und

- dadurch, Bereitstellen einer Leistungsausgangs über den zwei Enden der sekundären Wicklung (19) .

6. Verfahren nach Anspruch 5, das außerdem umfasst: Bereitstellen des Leistungseingangs als wesentlich größer als 3,3 Volt, und Bereitstellen des Leistungsausgangs als geringer als oder im Wesentlichen gleich 3,3 Volt.

7. Verfahren nach Anspruch 5, das außerdem umfasst: Bereitstellen des ersten Abschnitts der sekundären Wicklung (19) als entweder in Rechtsrichtung oder in Linksrichtung um einen der Schenkelabschnitte gewunden, und um den verbleibenden Schenkelabschnitt in entgegengesetzter Richtung, und Bilden eines Zentralabzweigs entlang der sekundären Wicklung (19) zwischen den zwei Enden in Bezug darauf.

8. Verfahren nach Anspruch 7, das außerdem umfasst: Bereitstellen einer dritten Wicklung mit zwei Enden und als gewunden um den Zentralabschnitt (14), aneinander koppeln der zwei Enden der sekundären Wicklung (19), um einen zweiten Knoten zu bilden, Koppeln eines der Enden der dritten Wicklung an den zweiten Knoten, und Bilden eines zweiten Leistungsausgangs von dem anderen Ende der dritten Wicklung, zusammen mit dem ersten Knoten.

9. Verfahren nach Anspruch 7, das außerdem umfasst: Bereitstellen einer dritten Wicklung mit zwei Enden und als um den Zentralabschnitt (14) gewunden, aneinander koppeln der zwei Enden der sekundären Wicklung (19), um einen zweiten Knoten zu bilden, Koppeln eines der Enden der dritten Wicklung an den zweiten Knoten, und Benutzen eines zweiten Leistungsausgangs in Bezug auf den ersten Knoten an dem anderen Ende der dritten Wicklung.

10. Verfahren nach Anspruch 5, das außerdem umfasst: Bereitstellen von wenigstens einem zusätzlichen Magnetkern mit wenigstens zwei Öffnungen, die einen Zentralabschnitt (14) dazwischen begrenzen, und zwei Schenkelabschnitten (16a, 16b), Bereitstellen des ersten Abschnitts der primären Wicklung als entweder in Rechtsrichtung oder in Linksrichtung um einen der Schenkelabschnitte des wenigstens einen zusätzlichen Magnetkerns gewunden, und Bereitstellen des zweiten Abschnitts der primären Wicklung (18) als in der entgegengesetzten Richtung um den anderen Schenkelabschnitt des wenigstens einen zusätzlichen Magnetkerns gewunden.

11. Verfahren nach Anspruch 10, das außerdem umfasst: Bereitstellen des ersten Abschnitts der sekundären Wicklung (19) als entweder in Rechtsrichtung oder in Linksrichtung um einen oder beide Schenkelabschnitte gewunden, und Bereitstellen eines ersten Abschnitts einer anderen sekundären Wicklung als um einen der Schenkelabschnitte des wenigstens einen zusätzlichen Magnetkerns in derselben Richtung wie der erste Abschnitt der sekundären Wicklung (19) gewunden, wobei die andere sekundäre Wicklung zwei Enden aufweist, die parallel zu den zwei Enden der sekundären Wicklung (19) gekoppelt sind.

Revendications

1. Transformateur destiné à fournir une faible tension de sortie, comprenant :

- un noyau magnétique (12) comportant au moins deux ouvertures définissant une portion centrale (14) entre elles et deux portions de jambe (16a, 16b) ;

- un enroulement primaire (18) comportant une première portion enroulée autour de l'une desdites portions de jambe soit dans le sens droit soit dans le sens gauche, et une seconde portion enroulée autour de l'autre portion de jambe dans le sens opposé formant une entrée de puissance ; et

- un enroulement secondaire (19) comportant une première portion enroulée autour de l'une desdites portions de jambe d'une fraction de tour, ledit enroulement secondaire (19) comportant deux extrémités formant une première sortie de puissance.

2. Transformateur selon la revendication 1, dans lequel ladite première portion dudit enroulement secondaire (19) est enroulée autour de l'une des portions de jambe soit dans le sens droit soit dans le sens gauche et autour de la portion de jambe restante dans le sens opposé, où un premier noeud disposé sur ledit enroulement secondaire (19) entre lesdites deux extrémités forme un branchement central par rapport à celles-ci.

3. Transformateur selon la revendication 2, comprenant en outre un troisième enroulement enroulé autour de ladite portion centrale (14), ledit troisième enroulement comportant deux extrémités, où lesdites deux extrémités dudit enroulement secondaire (19) sont couplées ensemble pour former un second noeud, où l'une desdites extrémités dudit troisième enroulement est couplée audit second noeud, et où l'autre extrémité dudit troisième enroulement forme une seconde sortie de puissance par rapport audit premier noeud.

4. Transformateur selon la revendication 3, dans lequel ledit troisième enroulement est enroulé autour de ladite portion centrale (14) d'une fraction de tour.

5. Procédé destiné à fournir une faible tension de sortie, comprenant les étapes consistant à :

- fournir un noyau magnétique (12) comportant au moins deux ouvertures définissant une portion centrale (14) entre celles-ci et deux portions de jambe (16a, 16b) ;

- fournir une première portion d'un enroulement primaire (18) comme étant enroulée autour de l'une desdites portions de jambe dans l'un parmi le sens droit ou le sens gauche ;

- fournir une seconde portion dudit enroulement primaire (18) comme étant enroulée autour de l'autre portion de jambe dans le sens opposé ;

- appliquer une entrée de puissance audit enroulement primaire (18) ;

- fournir un enroulement secondaire (19) ayant deux extrémités ;

- fournir une première portion dudit enroulement secondaire (19) comme étant enroulée autour de l'une ou des deux desdites portions de jambe d'une fraction de tour ; et

- fournir ainsi une sortie de puissance aux bornes desdites deux extrémités dudit enroulement secondaire (19).

6. Procédé selon la revendication 5, comprenant en outre les étapes consistant à fournir ladite entrée de puissance à une valeur sensiblement supérieure à 3,3 volts, et fournir ladite sortie de puissance à une valeur inférieure ou sensiblement égale à 3,3 volts.

7. Procédé selon la revendication 5, comprenant en outre les étapes consistant à fournir ladite première portion dudit enroulement secondaire (19) pour être enroulée autour de l'une des portions de jambe soit dans le sens droit soit dans le sens gauche et autour de la portion de jambe restante dans le sens opposé, et pour former un branchement central le long dudit enroulement secondaire (19) entre lesdites deux extrémités par rapport à celles-ci.

8. Procédé selon la revendication 7, comprenant en outre les étapes consistant à fournir un troisième enroulement comportant deux extrémités et étant enroulé autour de ladite portion centrale (14), coupler lesdites deux extrémités dudit enroulement secondaire (19) ensemble pour former un second noeud, coupler l'une desdites extrémités du troisième enroulement audit second noeud et former une seconde sortie de puissance à partir de l'autre extrémité dudit troisième enroulement, conjointement avec ledit premier noeud.

9. Procédé selon la revendication 7, comprenant en outre les étapes consistant à fournir un troisième enroulement comportant deux extrémités et étant enroulé autour de ladite portion centrale (14), coupler lesdites deux extrémités dudit enroulement secondaire (19) ensemble pour former un second noeud, coupler l'une desdites extrémités du troisième enroulement audit second noeud et prélever une seconde sortie de puissance par rapport audit premier noeud à l'autre extrémité du troisième enroulement.

10. Procédé selon la revendication 5, comprenant en outre les étapes consistant à fournir un noyau magnétique additionnel comportant au moins deux ouvertures définissant une portion centrale (14) entre elles et deux portions de jambe (16a, 16b), fournir ladite première portion dudit enroulement primaire (18) comme étant enroulée autour de l'une desdites portions de jambe dudit au moins un noyau magnétique additionnel dans l'un parmi ledit sens gauche ou sens droit, et fournir ladite seconde portion dudit enroulement primaire (18) comme étant enroulée autour de l'autre portion de jambe dudit au moins un noyau magnétique additionnel dans le sens opposé.

11. Procédé selon la revendication 10, comprenant en outre les étapes consistant à fournir ladite première portion dudit enroulement secondaire (19) comme étant enroulée autour desdites une ou deux desdites portions de jambe soit dans le sens droit soit dans le sens gauche, et fournir une première portion d'un autre enroulement secondaire comme étant enroulée autour de l'une desdites portions de jambe dudit au moins un noyau magnétique additionnel dans le même dit sens que ladite première portion dudit enroulement secondaire (19), ledit autre enroulement secondaire comportant deux extrémités couplées en parallèle auxdites deux extrémités dudit enroulement secondaire (19).

Drawing